1. Field of the Invention
The present arrangement relates to fiber optic cables. More particularly, the present arrangement relates to tight buffer type fiber optic cables.
2. Description of Related Art
In the field of fiber optic cables, one form of fiber arrangement includes an assembly for use in the interior of a building, such as an apartment or multi-dwelling unit. In this arrangement, there is no outer jacket around the fibers, but rather the interior parts of the fiber optic cable are included in the form of bundled fibers within subunits. For the purposes of this application a subunit is broadly defined as any independent fiber containing unit within the context of a larger fiber containing structure.
In place of a jacket for protection, the grouping of subunits is placed within an open or closed-top conduit tray. The tray is normally made from assemblies which are of various sizes and shapes (typically rectangular), some straight and some curved, secured to the wall with glue or other means of attachment, with a snap-on cover or lid. This assembly is considered an indoor assembly. In an exemplary arrangement, this assembly would be installed from a routing closet down a hall and into the dwellings with one fiber-subunit dropped off at each dwelling.
A typical subunit may include either one or more tight buffer optical fibers, several strength members such as aramid fibers and an outer subunit jacket. Any distribution cable arrangement as described above would typically include a plurality of such subunits, grouped into larger arrangements having seven or twelve subunits (i.e. six subunits around one subunit or nine subunits around three subunits which both would form substantially circular arrangements). These larger multi-subunit arrangements may then be stranded and bound to hold them together.
Such arrangements of bound subunits with no jacket are essentially based on designs taken from the internal components of typical jacketed cables, with the jacket simply being eliminated from the design. However, the design concerns of the internal components for a jacketed cable are different than those that are applicable to a jacketless assembly of bound subunits (for indoor overhead conduits). The internal components of a jacketed cable are typically arranged for addressing issues such as compression resistance, ability to bend within the jacket without attenuation, etc. . . .
For example, in the prior art, the lay length of the subunits and lay length of the binder existed for needs of a cable (with a jacket). In such prior art cables the lay length of the subunits would typically be 3-4 inches uni-directionally helical, with either no binder or with an overlapping mylar tape of about a 1 inch lay. Such an arrangement is prepared for robustness and not for mid-span entry, which is not a significant consideration in most cable designs.
In contrast to this, for jacketless assembly of bound subunits (for indoor overhead conduits), these issues are not as pressing. Rather, jacketless assemblies of bound subunits for indoor use, are primarily concerned with the robustness to be fed into overhead conduits (without coming apart) while being able to have frequent mid-span access to remove a subunit from the plurality of bound subunits in the arrangement.
As result of this situation, in the prior art when jacketless assemblies of subunits are simply designed based on the same criteria as the internal components of a jacketed cable, the arrangement and binding of the subunits is not particularly well suited for indoor use requiring frequent mid-span access.
These prior art cabling arrangements taken from jacketed designs makes it difficult or time consuming to break one individual tight buffer fiber subunit out of the subunit assembly (e.g. for connection and/or connectorization to some desired location).